Electric drill

ABSTRACT

An electrical drill for drilling oil and gas wells is disclosed. The electrical drill comprises a housing which accommodates a three-winding-phase electric motor with a cable lead-in powered through a supply line consisting of a two-wire cable line connected through said lead-in to said motor and a drill pipe string as the third wire of said supply. A device for testing insulation resistance of the circuit between the cable line and the motor winding is connected between one of the winding phases and said housing and mounted in the inner circular space thereof. The device for testing insulation resistance comprises a thyristor and a diode mounted in one frame having the form of a circular section for dissipating heat from said thyristor and diode and, simultaneously, providing electrical connection to said housing. This arrangement increases the rigidity of the lower end of the drill pipe string, increases the reliability of the entire installation and improves the dependability of the telemetering data obtained in the course of well boring.

United States Patent Grinchenko et a1.

[451 Sept. 19, 1972 1 ELECTRIC DRILL [72] Inventors: Nikolai NikolaevichGrinchenko, ulitsa Tonkopia, 24a, kv. 26; Vadim VyacheslavovichAbakanovich, ulitsa Lermontovskaya, 37, kv. 38; Jury MoiseevichGoldshtein, ulitsa 01minskogo, 17, kv. l; Grigory Zakharovich Gurevich,ulitsa Karelskaya, 14, kv. 39; Viktor Gavrilovich Chepelev, Moskovskyprospekt, 232a, kv. 10, all of Kharkov; Vladimir Zakharovich Kuvsliinov,ulitsa Gastello, 8, kv. 33, Moscow, all of U.S.S.R.

[22] Filed: June 4, 1971 [21] Appl. No.: 150,121

[52] US. Cl. ..324/54, 310/50, 310/66, 175/40, 174/47 [51] Int. Cl...G01r 31/12 [58] Field of Search ..310/80, 47, 68, 68 C, 66; 175/40;174/47; 166/65; 324/54 [56] References Cited UNITED STATES PATENTS3,546,502 12/1970 Botefuhr ..310/50 3,546,556 12/ 1970 Benkert ..3 10/502,993,391 7/ 1961 Raney ..3 10/50 Primary Examiner-J. D. MillerAssistant Examiner-R. Skudy Attorney-Waters, Roditi, Schwartz & Nissen[57] ABSTRACT An electrical drill for drilling oil and gas wells isdisclosed. The electrical drill comprises a housing which accommodates athree-winding-phase electric motor with a cable lead-in powered througha supply line consisting of a two-wire cable line connected through saidlead-in to said motor and a drill pipe string as the third wire of saidsupply. A device for testing insulation resistance of the circuitbetween the cable line and the motor winding is connected between one ofthe winding phases and said housing and mounted in the inner circularspace thereof. The device for testing insulation resistance comprises athyristor and a diode mounted in one frame having the form of a circularsection for dissipating heat from said thyristor and diode and,simultaneously, providing electrical connection to said housing. Thisarrangement increases the rigidity of the lower end of the drill pipestring, increases the reliability of the entire installation andimproves the dependability of the telemetering'data obtained in thecourse of well boring.

2 Claims, 4 Drawing Figures PATENTED SEP 19 I972 SHEET 1 0F 2 I L LgPATENTEUSEP 1 9 um ELECTRIC DRILL FIELD OF THE INVENTION The presentinvention relates to apparatus used for drilling oil and gas wells and,more particularly, to electrical drills.

BACKGROUND OF THE INVENTION the cable line. Special devices are usedwith the known electrical drills to connect one of the motor windingphases to the drill pipe string and enable the insulation resistance ofthe circuit between the cable line and the electric motor winding to betested relative to frame with the help of surface D.C. measuringinstruments. These devices form a separate section of the drill pipestring mounted directly above the electrical drill and consisting ofhousing portions which are threadably coupled to each other, a sealedcontainer with a switching assembly comprising two semi-conductorelements, a cable section and fastenings.

The cable section of this device terminates at one end in a two-pointreceptacle for connection to the supply cable and, at the other end, ina three-point receptacle for connection to the electric drill motor.

The presence of an additional device for insulation resistancemeasurement directly above the electrical drill in the drill pipe stringassembly has a number of disadvantages. Firstly, it affects the rigidityof the lower end of the pipe string and, therefore, lowers theeffeciency of the heavy drill pipes which is highly undesirable forcorrect well boring. Secondly, it results in the fact that thetelemetering system used for checking the well trajectory and makinggeophysical tests is removed from the well by a distance equal to thelength of the device, which markedly affects the trustworthiness of thetelemetering data.

Moreover, the overall reliability of the entire drilling installation isaffected to the presence of an additional element made up of a largenumber of assemblies and parts, including a cable section of a highlycomplicated design.

OBJECTS OF THE INVENTION It is the object of the present invention toprovide an electrical drill wherein the insulation resistance of thecircuit between the cable line and the electric motor winding to betested without the use of additional technical facilities forming aseparate section of the drill pipe string.

With this object in view, the electrical drill comprises a housing whichaccommodates a three-winding-phase electric motor with a cable lead-in,powered through a supply line. The supply line consists of a two-wirecable line connected through said cable lead-in to said motor and adrill pipe string forming the third wire cable line. A device fortesting insulation resistance of the circuit between the cable line andthe motor winding, is connected between one of the winding phases andsaid housing and mounted inside the inner circular space of the thereof,said device comprising a thyristor and a diode mounted in one framehaving the form of a circular sector for dissipating heat from saidthyristor and diode and simultaneously providing their electricalconnection with said housing.

In addition to the frame of the device for testing insulation resistancehas at one butt end, ears with holes for attachment of the device to aninner circular butt surface of said housing, and a contact tip locatedat the opposite butt end of said frame for connection with one of thephase winding leads of the electric motor, said contact tip beinginsulated from said frame but electrically connected with the bus-barinterconnecting the cathode of the thyristor and the anode of the diode,whilethe two other electrodes of these elements are connected to theframe of the device.

Such arrangement eliminates the need of an additional section in thedrill pipe string thereby increasing the rigidity of the lower end ofthe pipe string, and brings the telemetering system checking the welltrajectory nearer to the well, whereby increasing the trustworthiness ofall measurement data.

DESCRIPTION OF THE DRAWING This and other objects and advantages of thepresent invention will be better understood from the followingdescription of the specific embodiment of the invention when read inconnection with the accompanying drawings in which:

FIG. 1 is a drawing of an electrical drill, according to the invention;

.FIG. 2 is'a sectional view taken on line IIlI of FIG.

FIG. 3 is a drawing of the device for testing insulation resistance,according to the invention;

FIG, 4 is a schematic diagram of the device for testing insulationresistance.

SPECIFIC DESCRIPTION The electrical drill as seen in FIG. 1 comprises ahousing made up of a compensator housing 1, an upper housing 2, a statorhousing 3 and a spindle housing 4 threadably coupled to each other.

A cable lead-in 8 secured with the help of a holder 5 by bolts 6 inslide blocks 7 of the housing 1 has a twopoint receptacle 9 forconnection to a cable line mounted in the drill pipe string (not shownin the drawing). A semi-conductor device 12 for testing insulationresistance is mounted in the inner circular space of the housing 2 bymeans of bolts 10 and spring washers II. The frame of said device beingshaped as a circular sector (FIG. 2). The outer diameter of the frame ofthe device 12 is smaller than the inner diameter of the housing 2 whileits inner diameter is larger than the outer diameter of a jacket 13 ofthe hydro-protection system (not shown in the drawing), which seals ashaft 14 of the motor coupled to a shaft 15 of the spindle. A contacttip 16 of the device 12 is connected by means of a sleeve 17 to one ofthe phase-leads 18 of a stator winding 19 of the electrical drill motor,while two other phase leads and 21 are connected through a sealed holein the housing 2 to the cable lead-in 8.

A recess in the frame 22 (FIG. 3) shaped as a circular sectoraccommodates a diode 23 and a thyristor 24 of the tablet type, the diode23 being connected to the frame 2 through its cathode and the thyristor24 through its anode. The two other electrodes of these elements areinterconnected by a bus-bar 25 to which a contact tip 16, insulated fromthe frame 22 by a bush 26, is connected. Placed on the bus-bar 25 abovethe diode 23 and thyristor 27 are washers 27 and 28 made of mechanicallystrong and rigid dielectric material. Mounted on the washers are disksprings 29 which ensure a reliable contact between the diode 23 andthyristor 24 and the bus-bar 25 on one side and the elements 23 and 24and the frame 22 on the other when covers 30 are secured by screws 31.The washer 28 has a radial slot on the surface facing the bus-bar 25which, in its turn, has a hole located centrally with respect to thethyristor 24. A centrally located control electrode 32 of the thyristor24 isolated from the bus-bar 25 is brought out through the hole in thebus-bar 25 and the slot in the washer 28. The control electrode 32 isconnected to one of the leads 33 of a capacitor 34 mounted in the recessof the frame 22. A second lead 35 of the capacitor 34 is connected tothe frame 22 by a screw 36. The device 12 is attached to the inner buttsurface of the outer housing of the electrical drill by means ofsymmetrical ears 37 with holes 38 located on one butt end of the frame22. If necessary, the diode 23 and thyristor 24 may be sealed by fillingthe inner space of the device with epoxy compound after assembly.

FIG. 4 shows the connection of the electrical drill to the supplysystem.

In a supply unit 39 of the electrical drill motor 40 a phase 41 isconnected to the drill pipe string ground) having a third cable line.The phases 42 and 43 of the unit 39 are connected to the two-wire cablelead-in 8 of the electrical drill through a two-wire cable line 44mounted in the drill pipe string, while a lead 18 of the electricaldrill is connected through the device 12 to the frame (ground"). Aninstrument 45 is used to check insulation resistance when the system isdeenergized.

The arrangement described above operates as follows. .When theelectrical drill motor 40 is supplied with AC. working voltage all threewinding phases of the motor 40 are normally traversed by current, thenegative halfwave from the side of the switched phase being passed bythe diode 23, the positive half-wave, by the thyristor 24, the controlelectrode 32 of which is energized from the capacitor 34.

When the system is de-energized (for insulation resistance measurement)a DC. test voltage of a low power is applied from the surface measuringinstrument 45 to one of the phases of the cable line while the otherpole of the instrument 45 is grounded. At this time the followingpolarity requirements are observed: the positive pole of the instrumentis applied to the cable, the negative pole, to ground. The diode 23 isunable to pass current of such polarity. The thyristor 24 also remainsnon-conductive as the capacitor 34 does not pass direct current.

In this way a switching assembly cut off for the test current is broughtinto the circuit of the switched pha s between the motor-winding and theframe groun whereby enabling the insulation resistance of the systemwith respect to the frame (ground) to be tested.

What is claimed is:

1. An electrical drill comprising: a housing; a threewinding-phaseelectric motor with a wound stator, a rotor, a cable lead-in within saidhousing, said motor being powered through a wire supply line comprisedof a two-wire cable line connected through said lead-in to said motorand a drill pipe string forming said third wire; a device for testinginsulation resistance of a circuit between the cable line and thewinding of said motor, connected between one of the motor winding phasesand said housing and mounted in an inner circular space of said housing;a frame having the form of a circular sector; and a thyristor and diodemounted in said frame for dissipating heat from said thyristor and diodeand, simultaneously, providing their electrical connection to saidhousing.

2. An electrical drill as of claim 1, wherein said frame includes twobutt ends, one of said butt ends including a pair of butt end ears, eachprovided with a hole at one butt end, for attachment of an innercircular butt surface of the housing, a contact tip for connection withone of the winding phase leads of said electric motor located at theother of said butt ends, said contact tip being insulated from saidframe; a bus-bar electrically connected to said tip, interconnecting thecathode of said thyristor and the anode of said diode, the other twoelectrodes of said thyristor and diode being connected to said frame.

1. An electrical drill comprising: a housing; a three-windingphaseelectric motor with a wound stator, a rotor, a cable leadin Within saidhousing, said motor being powered through a wire supply line comprisedof a two-wire cable line connected through said lead-in to said motorand a drill pipe string forming said third wire; a device for testinginsulation resistance of a circuit between the cable line and thewinding of said motor, connected between one of the motor winding phasesand said housing and mounted in an inner circular space of said housing;a frame having the form of a circular sector; and a thyristor and diodemounted in said frame for dissipating heat from said thyristor and diodeand, simultaneously, providing their electrical connection to saidhousing.
 2. An electrical drill as of claim 1, wherein said frameincludes two butt ends, one of said butt ends including a pair of buttend ears, each provided with a hole at one butt end, for attachment ofan inner circular butt surface of the housing, a contact tip forconnection with one of the winding phase leads of said electric motorlocated at the other of said butt ends, said contact tip being insulatedfrom said frame; a bus-bar electrically connected to said tip,interconnecting the cathode of said thyristor and the anode of saiddiode, the other two electrodes of said thyristor and diode beingconnected to said frame.